The term "during the render of the page" is somewhat misleasing. The alerts are generated during the setup-render phase of an embedded component. The exact use case is a component whose rendering is effected by users's settings. There can be misconfigurations (related to conflicts between session state and persisted settings) that lead to a message being displayed to the user. As the component detects that error itself, it registers an alert with the alert manager. But if the alerts component is contained in the layout component, its begin-render phase (which generated the client-side JS for the alerts to be shown) is executed before the component's setup-render, so the messages are not added.

Jochen Kemnade
added a comment - 12/Jun/12 06:51 The term "during the render of the page" is somewhat misleasing. The alerts are generated during the setup-render phase of an embedded component. The exact use case is a component whose rendering is effected by users's settings. There can be misconfigurations (related to conflicts between session state and persisted settings) that lead to a message being displayed to the user. As the component detects that error itself, it registers an alert with the alert manager. But if the alerts component is contained in the layout component, its begin-render phase (which generated the client-side JS for the alerts to be shown) is executed before the component's setup-render, so the messages are not added.